1. Field of the Invention
The present invention relates to a system and a method in which sample treatment steps, including a solvent replacement step, are automated and performed in various analytical instruments, such as nuclear magnetic resonance (NMR) spectrometers, mass spectrometers, and spectroscopic instruments.
2. Description of the Related Art
In an NMR spectrometer, for example, it is always necessary to dissolve a sample under investigation in a deuterated solvent (e.g., deuterated chloroform, deuterated acetone, or deuterated water) or in a conventional protonated solvent containing more than a given amount (10% ) of a deuterated solvent. One reason for this is that the deuteration is necessary for the NMR lock that stabilizes the instrument. Another reason is to prevent appearance of excessively strong NMR signals due to protonated (non-deutereated) solvent, such as chloroform, acetone, or H2O; otherwise, the strong signals would overlap a signal of interest or the detection sensitivity would deteriorate. However, in high performance liquid chromatography (HPLC) or other similar technique, a protonated solvent is generally used as a mobile phase and so it is not easy to replace the protonated solvent by a deuterated solvent. Consequently, it is necessary that the protonated solvent is evaporated off, the sample is dried and solidified, and then is redissolved in a deuterated solvent. In the past, all of these sample pretreatment steps have been done by a human. That is, cumbersome manual operations have been performed.
In order to investigate samples by an NMR spectrometer by the prior art method, the samples must be processed with the following procedure.
(1) Samples collected in a fraction collector from a high performance liquid chromatograph are injected into sample containers.
(2) To remove the protonated solvent from each sample, it is evaporated, dried, and solidified.
(3) A given amount of deuterated solvent is dispensed.
(4) To mix the sample and the deuterated solvent well, the container is vibrated or the mixture is stirred.
(5) The sample dissolved in the deuterated solvent is transferred to a sample tube for NMR measurement.
(6) A label is stuck on the sample tube, and an NMR measurement is performed.
During the sequence of processing described above, when the step (1) is being executed, one must wait until all the samples are injected. Where one sample is taken in 15 minutes by fraction collection, one must wait for 24 hours if 96 samples are collected. If 192 samples are collected, one must wait for 48 hours. In this way, it takes a long time to pretreat samples. Furthermore, the steps (2)-(6) require cumbersome manual operations.